1. Field of the Invention
This invention relates to the field of electronic devices, which can be used to provide asset-tracking capability with global coverage for an extensive period of time.
2. Description of the Prior Art
Existing systems for asset tracking lack the capability required for long duration, global coverage due to several serious shortcomings. First, currently each asset-tracking device must be connected either to a battery, such as the battery of a vehicle, or an external power source such as the cigarette lighter adapter or an AC power supply. For asset tracking at the global scale, a battery connection or a direct AC power supply may not be always available and thus the power source becomes a major problem and limitation.
Some assets to be tracked may be in transit for an extended period of time. A device installed on such assets would require extensive duration since external power may be unavailable. For example, containers that are shipped overseas may need to run on internal batteries for two months or even longer. Simply adding batteries to an existing pack is not an ideal solution for durable tracking since this would enlarge the pack to an undesirable, bulky size.
Second, another major limitation of existing GPS tracking systems is the need to have an external GPS antenna with “Line of Sight” access to GPS satellites. For vehicle tracking, this may not be a major concern since vehicles primarily run on the surface of the earth with sufficient sky exposure. For tracking assets such as containers, it may not be possible to ensure reliable, constant satellite exposure. For instance, containers tend to be stacked up one on top of another during shipment. Also, a trailer may be kept inside a covered structure over a long period of time. If GPS data is not available, the location cannot be obtained from the satellites. Current GPS-based tracking systems at best can report the last available GPS reading, which may be beyond any reachable range from the actual current location.
Third, all current GPS-based tracking devices on the market use only one method of wireless communication to transmit location data between the asset and a centralized facility. For example, some tracking-service providers use the CDPD network of AT&T or local cellular networks. A typical problem with the single-network mechanism is that often the device is out of the coverage area of the wireless communication network. Currently, no wireless communication network offers complete global coverage.